The present invention relates to a reservoir tank for storing a reserve of propellant hydraulic fluid for a hydraulically driven cooling fan for an internal combustion engine and also a reserve of actuating fluid for a power steering system in an automotive vehicle, and more particularly relates to a dual type reservoir tank for the abovementioned two purposes which provides intercooling between said two fluid reserves, so as to be able to provide adequate cooling for said cooling fan propellant hydraulic fluid.
It is already known as shown, for example in, Japanese Utility Model Laying Open Publication No. 47-29026 (1972) and in Japanese Patent Laying Open Publication No. 58-13119 (1983) to propel a cooling fan for an internal combustion engine of an automotive vehicle or the like by a hydraulic motor.
However, there is a problem with regard to such a hydraulic motor driven engine fluid for the hydraulic motor rises at a relatively high operating temperature, since its viscosity is thereby reduced, the efficiency of the cooling fan motor is deteriorated, and the rotational speed of the cooling fan drops, and the internal combustion engine may not be properly cooled. Accordingly, conventionally there has been provided a cooling device in the hydraulic circuit for the propellant hydraulic fluid for the motor for the cooling fan. However, the provision of such a cooling device increases the flow resistance of this hydraulic circuit and therefore the pressure losses therein, and accordingly in any case deteriorates the efficiency of the system as a whole. Further, the piping work for the system is increased in complexity, and the system occupies more space within the engine room of the automotive vehicle; and, as a matter of course, costs are increased.